As noted before, concrete doesn't dry out to harden, it
When pouring concrete directly on the soil, the soil must be damp to ensure proper curing. However, when the soil is saturated with water, it is too wet and could adversely affect the concrete curing process.
It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
It is important to keep in mind that dry-pour concrete may not offer the same level of strength and durability as wet-mix concrete. Dry-pour concrete can also be more prone to cracking and shrinkage, which can lead to structural issues and the need for costly repairs over time.
Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
Keeping concrete moist is essential to the concrete curing process, but too much water and the concrete may not form in the way it needs to. If it loses too much moisture through evaporation, it will not cure properly and will become prone to cracks.
Water facilitates the curing and hardening processes. Without it, the chemical reactions needed to form the hard crystals that give the concrete its strength can't take place. Too little water leads to structurally weak concrete, and too much will disrupt effective curing and cause flaking, shrinking, divots or cracks.
If the weight of the concrete deforms the dirt base in any way, the entire concrete structure will be flawed. All of that is not to say that it is impossible to pour concrete over dirt. You can absolutely do it successfully, but you need to follow a specific process.
Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.
If it dries too quickly, the surface of the concrete will be weak, and will be subject to spalling. Spalling happens when a weak surface layer of concrete allows water to infiltrate. The water freezes and breaks up the surface of the concrete.
DO spray new concrete with water. One of the most common methods for curing concrete is to hose it down frequently with water—five to 10 times per day, or as often as you can—for the first seven days. Known as “moist curing,” this allows the moisture in the concrete to evaporate slowly.
Water containing bicarbonate ions and carbon dioxide causes a reaction known as carbonation in concrete. This often happens in the presence of salts and acid rain. As the acidic substances lower the concrete's pH, the calcium carbonate within the aggregates dissolves and reduces the concrete's strength.
Corrosion of reinforcing steel and other embedded metals is the leading cause of deterioration in concrete. When steel corrodes, the resulting rust occupies a greater volume than the steel. This expan- sion creates tensile stresses in the concrete, which can eventually cause cracking, delamination, and spalling (Figs.
If water evaporates too quickly, it will weaken the finished product with stresses and cracking. To put it simply, the goal is to keep the concrete saturated during the first 28 days. The first 7 days after installation you should spray the slab with water 5-10 times per day, or as often as possible.
As long as you not planning to put anything heavy on it it will be OK. Dry pouring concrete can have dry pockets were water did not get to. Usually using dry pouring to make a drive way for car, garage is sufficient and possibly with some light bearing structures(open steel/wood Structures) .
Plan to pour concrete before 10 a.m. or after 8 p.m. in order to avoid the hottest part of the day. If you are concerned about the temperature while working on a summer project, consider pouring concrete at night to give the mixture the best chance to harden and cure before the sun comes up.
As a general rule, stay away from using sand as a subbase. You're better off using gravel; your concrete will last longer and have less of a chance of cracking over time.
Standard concrete floor slab thickness in residential construction is 4 inches. Five to six inches is recommended if the concrete will receive occasional heavy loads, such as motor homes or garbage trucks. To prepare the base, cut the ground level to the proper depth to allow for the slab thickness.
Gravel for Concrete
Depending on what the driveway will be used for, the base may need to be 4 to 12 inches. Ideally, 6 inches of crushed stone or gravel should be used for most driveways. Proper application requires that the driveway hole be dug out, and the soil has to be prepared.
Technically you can, but you really shouldn't pour concrete over grass. To maintain its tensile strength, concrete needs to be laid on a firm, even, and dry foundation. Grass and soil will naturally channel moisture into the concrete from below, which will likely result in it cracking over time.
The answer to the question “Can you concrete over weeds?” is “no.” It's impractical to pour concrete over weeds because the weeds may grow back and seed. However, there are some solutions. Use polymeric sand and a propane torch to get rid of weeds. Alternatively, you can use a chemical weed killer.
The general rule of thumb is that concrete takes about 28 days to dry for every inch of slab thickness. Within 24 to 48 hours, the concrete will be ready for foot traffic.
Bottom line: Cement is a powdered ingredient used to make concrete. Concrete is the material used to make sidewalks, driveways and buildings. Sakrete makes a number of different concrete formulations in varying strengths and set times to meet the needs of different job requirements.
Effects of too much mixing water
Lower compressive strengths. Segregation of the concrete mix under certain conditions resulting in variable quality throughout the concrete mass. Cracking - with too much water, there will be lower tensile strength, and a tendency towards high shrinkage and subsequent cracking.